TABLE 8:

Forces calculated using F = Q′P/c, with appropriate Q′ values derived from the literature (see the text).

	Power (mW)	Force (pN)
		Q′ = 0.0341	Q′ = 0.012	Q′ = 0.09	No Q′
Mesostoma spermatocyte	15–23	1.7–2.6
Crane-fly spermatocyte	56–85	6.3–9.6
PtK2 pole movement	7.8		0.31	2.34
PtK2 anaphase chromatid movementa (Liang et al. 1991)	36	4
Theoretical force values	N/A				0.06–10
Previously measured value	N/A				700

The theoretical and previously measured force values are included for comparison. N/A, not applicable.

^aA trap of 60 mW to chromatid arms at the start of anaphase reversibly stopped anaphase chromatid movement. The authors used 60 mW measured at the objective, and because of the 60% transmission of the lens, the power was 36 mW at the specimen.